Process of making monobromo indigo.



Process of UNITED STATES PATENT oFF o'E.

GADIENT ENGI, OFBASEL, SWITZERLAND, ASSIGNOR TO THE FIRM OF SOCIETY OF CHEMICAL INDUSTRY IN BASLE, OF BASEL, SWITZERLAND.

PRQCESS OF MAKING MONOBROMO INDIGO.

' No. ass,2so.

Specification of Letters Patent.

Patented May 19, 1908.

.To all whom it may concern:

Be it known that I, GADIENT ENGI, doc tor of philosophy and chemist, a citizen of the Swiss Republic, and resident of "Basel, Switzerland, have invented a new and useful Making lIonobromo Indigo, of which the following is a full and exact specification.

In my applications for United States Patent Ser. No. 364019 & 364020, filed March 23 1907, I described the manufacture .of triand tetrabromoderivatives of indigo conslstinfilin treating indigo, mono-"or dibromindigo in go at araised tem er'ature with the appropriate proportion of romin in presence of a suitable indifferent diluent or solvent, par ticularly of nitrobenzene.

I have found that this proces may also be applied advantageously for producing a monobromoderivative of indigo, the heating of indigo with the theoretically necessary quantity of bromin (2 atomic proportions), in

resume of nitrobenzene furnishing a monoromoderivative in a very purefcondition and with a quantitative out-put.

By employing are theoretmally necessary gpantity of bromin, the new process gives 'rectly a mono-bromo-indigo containing the exact percentageof-bromin (about 24% of Br.) and corresponding to the formula 1. 9 32 1- Example: 5 parts of indigo, parts of nitrobenzene and 3' parts (2 atomic roportions) of bromm *is dyed are well mixed toget er and heated in a reflux apparatus in an oil bath in such a manner that the temperature of the latter rises to 225 C. in the course of about an hour; the temperature of the bath is then maintainedat 226-228 C. for about 1-2 hours, much hydrogen bromid bein evolved. After cooling and filtering the solid monobroino-derivative of inch 0 is washed with alcohol and dried; it is tus obtained as a beautiful. blue crystalline powder, in nearly quantitative yield and of satisfactory purity, containing about 24% bromid (theoretical quantity of bromin 23.5%)

When treated with alkaline reducing agents, the new product yields easily and smoothly a bright yellow vat, wherein cotton blue tints which are considerably redder, more vivid and faster to washing and to chlorin than the tints obtained in vats prepared from the I monobromo-derivative nown in commerce as Indigo R.

What I claim is:

The herein described process for the manufacture of a monobromoderivative of indigo by heating indigo with two atoms of bromin in resence of nitrobenzene.

n witness whereof I have hereunto signed name this 11 day of March 1907, in the of two subscribing witnesses.

GADIENT ENGI.

y presence Witnesses Gno. GIFFORD, AMAND BRANN'. 

